In light of the increasing threat of terrorism, improved explosive detection systems and methods are urgently needed for use at security checkpoints, such as those located at airports and other transportation hubs. While there are several liquid explosives, such as nitroglycerine and picatinny liquid explosive (PLX), that could be used to bring down an aircraft, these liquid explosives are generally too unstable or too easily detected to be readily smuggled aboard. Terrorists are more likely to use two or more liquids that are stable by themselves, but which form a powerful explosive when mixed together. A prime candidate for this approach would be triacetone triperoxide (TATP). The raw ingredients of TATP are liquids that could potentially be carried on board in sufficient quantities in containers such as bottles of shampoo or contact lens solution.
Because of the nature of liquid binary explosives, detection based on particles on the surface of a container is difficult if not impossible. In addition, effective screening of liquid explosives requires the ability to detect the explosives in sealed containers. Although a number of devices have been developed for such purpose, they typically use a single detection technology that often produces false positive readings.
Accordingly, there still exist a need for container screening systems and methods with low false positive rate and high probability of detection.